Membranes in the mitotic apparatus (MA) may control the (Ca ions) and thus regulate the assembly and/or function of the motile elements. To seek a deeper understanding of membrane-Ca ions function, four areas of investigation are proposed: 1) The ultrastructure of MA-membranes will be examined in PtK-1 cells, Arbacia eggs, and Haemanthus endosperm using an OsO4-K3Fe(CN)6 post-fixation that stains the nuclear envelope (NE) and endoplasmic reticulum (ER). Electron microscopy (EM) will probe the pattern of membranes and structural associations between microtubules and ER, and the localization of ATPases. 2) Localization of membrane-bound Ca ions in living cells will be examined with chlorotetracycline (CTC). Haemanthus cells treated with anti-Ca ions-transport agents will be analyzed for changes in CTC fluorescence, spindle birefringence and chromosome motion. 3) (Ca ions) fluctuations during mitosis will be monitored with aequorin in conjunction with image intensification to determine if, when and where (Ca ions) increases occur. Ionophores and Ca ions buffers may help us define the critical (Ca ions) required for mitosis. 4) Ca ions as signals for hormonal activation of mitosis will be explored in Funaria protonemata that have been induced by cytokinin to form buds. Ca ions changes and localization associated with target cells will be determined using murexide absorption shifts, CTC fluorescence and 45Ca ions autoradiography. EM studies will correlate the Ca ions changes with the position and aggregation of membranes and organelles following cytokinin induction.